Method for improving the stainless steel surface finish on a composite metal laminate

ABSTRACT

The stainless steel surface of a strip of composite, rollbonded, stainless steel-aluminum laminate material is characterized by a matte finish and by considerable surface roughness but is shown to be provided with a high quality surface finish in an economical manner by advancing the metal laminate over spaced supporting rolls under substantial tension, by providing a series of buffing rolls formed of fabrics of moderate abrading properties and by rotating these buffing rolls in the direction of advance of the laminate on roll axes disposed normal to said direction of advance while oscillating the buffing rolls to a controlled limited extent along the roll axes and while pressing the buffing rolls against the stainless steel surface between the support rolls with substantial force for obtaining a selected degree of wrap of the laminate against surfaces of the buffing rolls to provide a substantial area of buffing engagement between the strip surface and the rolls, and by intermittently projecting abrasive particles of moderate abrading properties free of a gaseous carrier medium at a force in excess of 600 psi, substantially radially onto surfaces of the buffing rolls for penetrating the buffing rolls with the abrasive particles to a significant extent so that the abrasive particles are carried by the buffing rolls over the entire area of buffing engagement between the strip surface and the rolls, thereby to obtain an extensive degree of a moderate type of surface abrasion for achieving the desired high quality surface finish while using only limited quantities of expendable buffing and abrasive materials.

States Buchinski et a1.

atent 1 METHOD FOR IMPROVING THE STAINLESS STEEL SURFACE FINISH ON ACOMPOSITE METAL LAMINATE [75] Inventors: Joseph J. Buchinski, Wrentham;

Thaddeus Smietana, Attleboro, both of Mass.

[73] Assignee: Texas Instruments Incorporated,

Dallas, Tex.

[22] Filed: Nov. 17, 1972 [21] Appl. No.: 307,708

[52] US. Cl 51/328; 51/292 [51] Int. Cl. B24b 1/00 [58] Field of Search51/292, 281 R, 317, 318, 51/263, 264, 328. 39, 78

[56] References Cited UNITED STATES PATENTS 783,850 2/1905 Zucker 51/2631,998,770 4/1935 Schulte 51/324 X 3,277,609 10/1966 Horie 51/281 R X3,434,240 3/1969 Phelps... 51/39 X 3,581,439 6/1971 Jensen 51/328 X3,701,222 10/1972 Testolin 51/292 X [57] ABSTRACT The stainless steelsurface of a strip of composite, rollbonded, stainless steel-aluminumlaminate material is characterized by a matte finish and by considerablesurface roughness but is shown to be provided with a high qualitysurface finish in an economical manner by advancing the metal laminateover spaced supporting rolls under substantial tension, by providing aseries of buffing rolls formed of fabrics of moderate abradingproperties and by rotating these buffing rolls in the directionofadvance 0f the laminate on roll axes disposed normal to said directionof advance while oscillating the buffing rolls to a controlled limitedextent along the roll axes and while pressing the buffing rolls againstthe stainless steel surface between the support rolls with substantialforce for obtaining a selected degree of wrap of the laminate againstsurfaces of the buffing rolls to provide a substantial area of buffingengagement between the strip surface and the rolls, and byintermittently projecting abrasive particles of moderate abradingproperties free of a gaseous carrier medium at a force in excess of 600psi, substantially radially onto surfaces of the buffing rolls forpenetrating the buffing rolls with the abrasive particles to asignificant extent so that the abrasive particles are carried by thebuffing rolls over the entire area of buffing engagement between thestrip surface and the rolls, thereby to obtain an extensive degree of amoderate type of surface abrasion for achieving the desired high qualitysurface finish while using only limited quantities of expendable buffingand abrasive materials.

4 Claims, 2 Drawing Figures 1 METHOD FOR IMPROVING THE STAINLESS STEELSURFACE FINISH ON A COMPOSITE METAL LAMINATE In the past, the automotiveindustry had used stain less steel strip materials in making automotivetrim and, for these purposes, had required that the strip materialsdisplay a high quality surface finish corresponding to AISI Finish No. 8(a root mean square surface roughness of about 0.5 to 1.5 R.M.S.). Theunit of measurement of surface roughness as described herein is themicroinch as established by the American Standards Association, ASA B46.This quality of surface finish is easily obtained in solid stainlesssteel strip materials at very low cost by use of conventional rollingmill processes. However, the automotive industry is now makingautomotive trim from roll-bonded, composite, stainless steel-aluminumstrip material so that the aluminum component of the trim will providegalvanic corrosion protection for automotive bodies at the trimlocations on the bodies. It is found that the stainless steel surface ofsuch roll-bonded laminate material is characterized by a matte finishand by a surface roughness on the order of 20 R.M.S. and verysubstantial buffing has been required to provide the laminate withthehigh quality stainless steel surface finish required for automotive trimpurposes. The'costs associated with providing this high quality finishon the laminate by conventional buffing methods have been almostprohibitive.

It is an object of this invention to provide novel and improved methodsfor providing a composite, rollbonded stainless steel-aluminum laminatematerial with a high quality surface finish suitable for automotive trimpurposes; and to provide such methods which are convenient andeconomical to perform.

Other objects, advantages and details of the methods of this inventionappear in the following detailed description of preferrred embodimentsof the invention, the detailed description referring to the drawings inwhich:

FIG. 1 is a diagrammatic view illustrating the method of this invention;and

FIG. 2 is a partial section view to enlarged scale along line 22 of FIG.1.

In accordance with the present invention, it has now been recognizedthat, although the stainless steel surface of a roll-bonded, composite,stainless steelaluminum laminate strip material is normallycharacterized by a matte finish and by a surface roughness on the orderof 20 R.M.S., the stainless steel surface of the laminate material issubstantially free of major surface defects. Accordingly, it has beenfound that the high quality surface finish required for automotive trimpurposes is obtained on the stainless steel surface with suitableeconomy where a relatively moderate type of sur face abrasion is usedbut where this moderate type of abrasion is carried out to an extensivedegree while employing novel and advantageous procedures for minimizinguse of expendable abrading materials such as buffing pads and abrasivecompounds to keep the surface finishing costs low.

Referring now to the drawings, 10 in FIGS. 1 and 2 indicates a strip ofcomposite, roll-bonded stainless steel-aluminum laminate material asconventionally used in the manufacture of automotive trim. As will beunderstood, such laminate material is usually formed in a strip about 24inches wide and in 40-60 percentage ratio typically having a totalcomposite thickness of about 0.022 inches embodying a layer of stainlesssteel about 0.009 inches thick and a layer of aluminum about 0.013inches thick, these layer materials being metallurgically bondedtogether throughout the interfaces between the layer materials. Forexample, the stainless steel material usually comprises 434 StainlessSteel and the aluminum layer is formed of 5052 Alloy Aluminum.Alternately the aluminum layer of the composite may comprise severaldifferent aluminum materials metallurgically bonded together. Asroll-bonded, the stainless steel layer of the laminate typically has amatte finish and has a surface roughness of about 20 R.M.S. but issubstantially free of major surface defects of a depth greater thanabout 30 microinches. As will be understood, references herein to thedepth of major surface defects refers to the measurement from thehighest point at the edge of the defect to the level of the lowestportion of the defect area. As roll-bonded, the stainless steel layer ofthe laminate is usually in almost soft or annealed condition havingundergone only slight workhardening during roll-bonding of the stainless1 steel material to the aluminum layer of the laminate.

As shown in the drawings, the laminate material 10 is advanced from apay-off reel 12 between a pair of pass line or guide rolls 14, over aseries of supporting rolls 16, and between additional guide rolls 18 andis then coiled on a take-up reel 20, the take-up reel being driven withsufficient force relative to the drag imposed on the strip material 10by the pay-off reel 12 to establish a substantial tension in the stripmaterial. In a preferred embodiment of the method of this invention, forexample, the strip material is advanced at a speed from about 10 to feetper minute and is subjected to a tensile force of about 6000 pounds(about 1 1,000 psi for a strip of the noted cross-sectional dimensions)for drawing the strip 10 tautly over the supporting rolls 16. Thestainless steel surface 22 of the strip 10 is disposed in an upwardlyfacing direction as viewed in FIGS. 1 and 2.

In accordance with this invention, the strip 10 may be advanced from theguide rolls 14 between a pair of pressing pads 24 which have relativelysoft fabric surfaces 26 held lightly against the strip for wipingextraneous materials such as dust and dirt from the strip surfaces.However, these pads may be omitted where the strip material issubstantially free of such extraneous matter. The strip 10 is thenadvanced beneath six buffing rolls 28, 30, 32, 34, 36 and 38 each ofwhich is located between a pair of supporting rolls l6 and each of whichis pressed against the stainless steel surface of the strip 10 withsufficient force so that the strip 10 wraps against a substantialsurface area of each of the buffing rolls as shown in FIG. 2 to providea substantial area of buffing engagement between the strip and buffingrolls. Typically, for example, where the buffing rolls have a diameterof about 18 inches and a lateral length of engagement with the strip 10of about 24 inches, and where the strip 10 is tensioned as described inthe example set forth above, the buffing rolls are pressed against thestrip 10 with a force of at least about 1000 pounds so that the stripwraps an arc of between 20 and 40, and preferably wraps an arc of atleast about 5, on the surface of each of at least the buffing rolls 28,30, 32 and 34.

as is indicated by the arrow 40 in FIG. 2. In addition, 7

each of the buffing rolls is oscillated along the axes of the buffingrolls by any conventional means (not shown) as is indicated by thearrows 42 in FIG. 1, these buffing roll axes each being disposed normalto the di-' rection of movement of the strip 110 as is illustrated inFIG. 1. The buffing rolls are rotated at a sufficient speed to achieve arelative speed or linear speed of engagement between the buffing rollsurface and the stainless steel surface of the strip it), the relativespeed of the buffing roll and strip surfaces therefore being equal toabout 141 feet per second less the speed of advance of the strip 10 onthe order of 100 to 150 feet per second. Typically, for example, wherethe buffing rolls have a diameter of about 18 inches, the buffing rollsare rotated at a speed of about l800'rpm to achieve a linear surfacespeed of about l4l feet per second at the area of engagement with thestrip 10. The speed of rotation of the buffing rolls may be adjustedduring wear of the buffing rolls to substantially maintain this surfacespeed. Most importantly, in the process ofthis invention, theoscillation of the buffing rolls is controlled to be selectively limitedin extent relative to the frequency of the oscillation so that, with therelatively extensive degree of moderate abrasion utilized in the processof this invention, no visible buffing patterns are formed on thestainless steel surface of the strip by the buffing roll oscillation. Itis found, for example, that the oscillation of the buffing rolls shouldbe at least about one-fourth inches (as measured between extreme limitsof movement of such oscillation) but should be limited to aboutthree-fourths inches in length and at a frequency from 50 to200oscillations per minute. Typically, for example, the buffing rollsare oscillated one-half inches at a frequency of 180 oscillations perminute.

In accordance with the method of this invention, the materials employedin the buffing rolls 28, 3t), 32, 34, 36 and 38 are characterized asdisplaying moderate abrading properties. That is, the materials of thebuffing rolls are selected such that they are adapted to cut thestainless steel surface of the strip 10 to a depth of as much as 10microinches but are not adaptedto cut this stainless steel surface to adepth greater than about 20 to microinches. Typically, for example, thebuffing rolls 28 and 30 are each made up by round buffing pads eachcomprising a layer of sisal fabric between two layers of cotton fabric,the sisal fabric embodying natural fibers loosely woven with five toseven groups of fibers per inch in each of two directions, the fabricbeing bias cut in conventional manner to dispose fiber ends obliquely tothe circumference of the buffing rolls, each of the fabrics having anoriginal sheet diameter greater than 18 inches with a large centeropening but being shirred or drawn in to form a pad of about 18 inchesouter diameter and several inches inside diameter. The sheet of cottonfabric used is about to inches in diameter with a large center openingand is shirred to form a pad of the same final diameter as the sisalfabric, the cotton fabric having 80 to fibers per inch in each directionover the fabric and having a weight 2.50 (2.5 square yards per pound),these cotton pad fabrics also preferably being bias cut as noted above.In this arrangement, where the strip 10 is about 24 inches wide, about40 to 50 0f the noted three layer A. buffingpadsare stackedinside-by-side relation in each of the buffing rolls 28 and 30 to form ahard-packed buffing roll. Typically, theibuffing rolls 32, 34, Zip and38 are then each made up of about 40 toSO 4-layer pads where each. layerof the pad comprises a layer of cotton fabric as above-described shirredand hardpacked in the buffing roll.

In accordance with this invention, moderateabrasive compounds are alsoused :in conjunction with the buffing rolls described above. That is,the abrasive compounds include chromium oxide and aluminum oxideabrasive particles of about minus 325 mesh size, the. W most abrasivecompound utilized in this invention com prising what is commonly calleda cut and color compound embodying abrasive particles consisting of'about one halfchromium oxide andone half aluminum oxide particles. I i

In addition, the method ofthis invention also utilizes a less abrasivecompound commonly called a color compound embodying a major proportionof chromium oxide particles and a substantially smaller portion ofaluminum oxide particles, the abrasive particles in this I g lattercompound also being about minus 325 mesh size.

' Typically, for example, these abrasive compounds'have of gaseouscarrier mediums substantiallyradially onto 7 the buffing rolls so thatthe abrasive compounds penea composition, by weight, of about 50 percentwater, about 15 percent fatty acids to serve as a compound binder andlubricant, and about 35 percent of the noted abrasive particles.

In an important part of this invention, the abovenoted moderate abrasivecompounds are supplied to selected buffing rolls by projecting theabrasive c'ompounds with very substantial force and without the usetrate the buffing roll materials to a significant extent. For example,in a preferred embodiment of this invention, the abrasive compounds areprojected by a "conventional airless spray mechanisrntnotshown).-at.pres sures in the range from about 600 to 1200 'psi.-fromnozzles closely spaced with respect to the buffingrolls;

the abrasive compound preferably being projected in;

termittently to minimize use of the abrasive compound. Typically, forexample, the abrasive compound described above as a cut and colorcompound is projected; from a pair of nozzles 44 spaced 8 to 12 inchesaway from each ofthe buffing rolls 28 and 30, theQnozzles being directedradially toward the buffing roll surfaces but being adapted to face outthe abrasive compound 46 so that the compound projected by two nozzles44 covers the full width of each of the buffing rolls'28 and 7 3t) andso that the buffing compound is directedinto a typical embodiment ofthis invention as thus far described above, the nozzles 44 and 48 areregulated by any conventional means (not shown) to direct the I notedabrasive compounds into the buffing rolls intermittently for durationson the order of 0.005 to 0.015 seconds and at a frequency of 2 to 3times per minute.

As illustrated in FIG. 1, abrasive compounds are preferably notprojected onto the buffing rolls 36 and 38 which perform a finalpolishing of the stainless steel surface of the strip 10.

In accordance with this invention, the strip is finally advanced betweena pair of pressure pads 52 which have soft fabric surfaces (not shown)thereon for wiping all abrasive compounds from the strip before coilingof the strip on the take-up reel 20.

Where the above-described buffing method has been utilized as described,roll-bonded composite stainless steel-aluminum strip material has beenprovided with a very high quality surface finish at very low cost. Forexample, where the laminate material having a stainless steel surface 24inches wide characterized by a matte finish and by a surface roughnessof R.M.S. was buffed using the buffing rolls and abrasive compoundsdescribed above as being preferred, where the two rolls were 18 inchesin diameter, were rotated at 1800 rpm., and were oscillated for adistance of one-half inch 180 times per minute, and where the rolls werepressed against the stainless steel surface with a force of 1000 poundsand were penetrated to a depth of about onehalf inch with the notedabrasive compounds projected at pressures of about 900 psi., the surfacefinish pro-- vided on the stainless steel surface exceeded the surfacequality required for automotive purposes even though the cost ofperforming the method was as little as one-quarter the cost of providingthis surface finish by conventional methods. In this arrangement, thesubstantial buffing pressures and speeds and substantial areas ofbuffing engagement utilized with the moderately abrasive materials wasfully effective to achieve the desired surface improvements. Thedisposition of the buffing rolls normal to the direction of advance ofthe strip materials, the prescribed limited degree of oscillation of thebuffing rolls and the substantial area of buffing engagement cooperateto avoid formation of buffing patterns even though substantial buffingforces are used, thereby avoiding the development of surface defectsthat would require additional buffing to remove, Further, the airlessspray projection of the abrasive compounds avoids wide dispersal andwaste of the abrasive compounds; the projection of the abrasivecompounds at high pressures to penetrate the buffing rolls to asignificant extent assures that the abrasive compound is carried by thebuffing rolls throughout the area of buffing engagement and assures mosteffective utilization of the abrasive compounds; the penetration of thepads with the abrasive particles effects maximum buffing results withminimum wear of the buffing pad materials. In this way, by accomplishingthe desired surface improvement while maximizing effective utilizationof expendable buffing pad and abrasive compound materials, the totalcost of performing the buffing process has been significantly improved.

It should be understood that although particular embodiments of themethods of this invention have been described in detail by way ofillustrating this invention, this invention includes all modificationsand equivalents of the disclosed embodiments falling within the scope ofthe appended claims.

We claim:

1. Method for providing a high quality surface finish corresponding toMS] Surface Finish No. 8 on the stainless steel surface of a compositeroll-bonded stainless-steel-aluminum-laminate strip material where saidstainless steel surface is characterized by a matte finish and by a rootmean square surface roughness of about 20 R.M.S. and is substantiallyfree of surface defects of a depth greater than about 30 microinches,said method comprising the steps of advancing said strip material over aseries of spaced supporting rolls under substantial tension with saidstainless steel surface facing away from said supporting rolls, rotatinga series of fabric buffing rolls of moderate abrading properties in thedirection of advance of said strip material on axes disposed normal tosaid direction of advance while oscillating said buffing rolls to acontrolled limited extent along said buffing roll axes and whilepressing said buffing rolls against said stainless steel surface withsufficient force between respective pairs of said supporting rolls forobtaining a wrap of an arc of between 20 and 40 of said tensioned stripmaterial against the peripheral surfaces of each of said buffing rollsto provide substantial areas of buffing engagement between saidstainless steel surface and said buffing rolls, and intermittentlyprojecting abrasive particles of moderate abrading properties free of agaseous carrier medium at a force in excess of about 600 pounds persquare inch substantially radially onto respective surfaces of saidfabric buffing rolls to penetrate said buffing rolls to a significantextent with said abrasive particles for assuring that said abrasiveparticles are carried by said buffing rolls throughout said areas ofbuffing engagement.

2. A method as set forth in claim 1 wherein said buffing rolls areoscillated on said buffing roll axes for a dis tance in the range fromone-fourth to three-fourths inches at a frequency in the range fromabout 50 to 200 oscillations per minute.

3. A method as set forth in claim 1 wherein said buffing rolls arerotated at a speed selected with respect to the speed of advance of saidstrip material to provide a linear speed of engagement between thebuffing rolls and said stainless steel surface in the range from aboutto feet per second.

4. Method for providing a high quality surface finish corresponding toAlSl Surface Finish No. 8 on the stainless steel surface of a composite24 inch wide rollbonded stainless-steel-aluminum-laminate strip materialwhere said stainless steel surface is characterized by a matte finishand by a root mean square surface roughness of about 20 R.M.S. and issubstantially free of surface defects of a depth greater than about 30microinches, said method comprising the steps of advancing the saidstrip material over a series of spaced supporting rolls undersubstantial tension on the order of 1 1,000 pounds per square inch withsaid stainless steel surface facing away from said supporting rolls,rotating a series of fabric buffing rolls of moderate abradingproperties at a selected surface speed in the range from 100 to 150 feetper second in the direction of advance of said strip material on axesdisposed normal to said direction of advance while oscillating saidbuffing rolls to a controlled limited extent in the range from onefourthto three-fourths inches at a frequency of 50 to 200 oscillations perminute along said buffing roll axes and while pressing said buffingrolls against said stainless steel surface with sufficient force betweenrespective pairs of said supporting rolls for obtaining a selecteddegree of wrap of an arc of at least about 20 of said tensioned stripmaterial against the peripheral surfaces of each of said buffing rollsto provide substantial areas of buffing engagement between saidstainless to a significant extent of at least about one-half inch l withsaid abrasive particles for assuring that said abrasive particles arecarried by said buffing rolls through: I

out said areas of buffing engagement.

1. Method for providing a high quality surface finish corresponding toAISI Surface Finish No. 8 on the stainless steel surface of a compositeroll-bonded stainless-steel-aluminumlaminate strip material where saidstainless steel surface is characterized by a matte finish and by a rootmean square surface roughness of about 20 R.M.S. and is substantiallyfree of surface defects of a depth greater than about 30 microinches,said method comprising the steps of advancing said strip material over aseries of spaced supporting rolls under substantial tension with saidstainless steel surface facing away from said supporting rolls, rotatinga series of fabric buffing rolls of moderate abrading properties in thedirection of advance of said strip material on axes disposed normal tosaid direction of advance while oscillating said buffing rolls to acontrolled limited extent along said buffing roll axes and whilepressing said buffing rolls against said stainless steel surface withsufficient force between respective pairs of said supporting rolls forobtaining a wrap of an arc of between 20* and 40* of said tensionedstrip material against the peripheral surfaces of each of said buffingrolls to provide substantial areas of buffing engagement between saidstainless steel surface and said buffing rolls, and intermittentlyprojecting abrasive particles of moderate abrading properties free of agaseous carrier medium at a force in excess of about 600 pounds persquare inch substantially radially onto respective surfaces of saidfabric buffing rolls to penetrate said buffing rolls to a significantextent with said abrasive particles for assuring that said abrasiveparticles are carried by said buffing rolls throughout said areas ofbuffing engagement.
 2. A method as set forth in claim 1 wherein saidbuffing rolls are oscillated on said buffing roll axes for a distance inthe range from one-fourth to three-fourths inches at a frequency in therange from about 50 to 200 oscillations per minute.
 3. A method as setforth in claim 1 wherein said buffing rolls are rotated at a speedselected with respect to the speed of advance of said strip material toprovide a linear speed of engagement between the buffing rolls and saidstainless steel surface in the range from about 100 to 150 feet persecond.
 4. Method for providing a high quality surface finishcorresponding to AISI Surface Finish No. 8 on the stainless steelsurface of a composite 24 inch wide roll-bondedstainless-steel-aluminum-laminate strip material where said stainlesssteel surface is characterized by a matte finish and by a root meansquare surface roughness of about 20 R.M.S. and is substantially free ofsurface defects of a depth greater than about 30 microinches, saidmethod comprising the steps of advancing the said strip material over aseries of spaced supporting rolls under substantial tension on the orderof 11,000 pounds per square inch with said stainless steel surfacefacing away from said supporting rolls, rotating a series of fabricbuffing rolls of moderate abrading properties at a selected surfacespeed in the range from 100 to 150 feet per second in the direction ofadvance of said strip material on axes disposed normal to said directionof advance while oscillating said buffing rolls to a controlled limitedextent in the range from one-fourth to three-fourths inches at afrequency of 50 to 200 oscillations per minute along said buffing rollaxes and while pressing said buffing rolls against said stainless steelsurface with sufficient force between respective pairs of saidsupporting rolls for obtaining a selected degree of wrap of an arc of atleast about 20* of said tensioned strip material against the peripheralsurfaces of each of said buffing rolls to provide substantial areas ofbuffing engagement betweEn said stainless steel surface and said buffingrolls, and intermittently projecting abrasive particles of moderateabrading properties free of a gaseous carrier medium at a force in therange from about 600 to 1200 pounds per square inch substantiallyradially onto respective surfaces of said fabric buffing rolls topenetrate said buffing rolls to a significant extent of at least aboutone-half inch with said abrasive particles for assuring that saidabrasive particles are carried by said buffing rolls throughout saidareas of buffing engagement.